What Causes the Light and Dark Areas on Radar Images of Asteroid 2015 TB145?

Question: Just saw the stunning images of asteroid 2015 TB145. These are images obtained by illuminating the asteroid with microwaves from a source nearly the same direction as the receiving antenna. Why does the asteroid appear to be illuminated from the side, instead of directly from the front?  — Steve

Answer: The light and dark areas on radar images of objects such as the asteroid 2015 TB145 are due to high and low reflectance of the radar signal off of the asteroid’s surface.  For example, the brighter areas are places where the radar signal reflectance is higher than it is in the darker areas.  This higher or lower reflectance can be due to ridges or other changes in the topography of the asteroid, or can also be due to changes in the roughness of the asteroid’s surface.

Jeff Mangum

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Questions About a Career in Astronomy

Question: I am a 12 year old girl and I love astronomy and I would love to become an astronomer when I grow up. I know it may seem that I am too young but i’m really interested in the subject. What skills does it require to become an astronomer and how many years does it take to earn a PhD in chemistry? I’m an Egyptian and there are no Egyptian astronomers. Is it possible to become an astronomer even though i’m Egyptian?  — Sarah

Answer: That is great that you are interested in being an astronomer!  Let me first point you to the Careers in Astronomy section of this blog.  There have been many questions just like the one you have asked regarding what it takes to have a career as an astronomer that I have answered in this careers section.  Note also that nationality plays no role in determining if a person can pursue a career in astronomy.  Astronomers come from all over the world (including Egypt).  If you have further questions about a career in astronomy after having looked through the information in the Careers in Astronomy section, let me know.

Jeff Mangum

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What Type of Antennas are Used with ALMA?

Question: Which type of antenna arrays are used in ALMA site?  — Aloka

Answer: You can get the answer to this question plus a lot more facts about the Atacama Large Millimeter/submillimeter Array at NRAO’s summary of ALMA.  The antennas used with ALMA are of two types: 12m and 7m diameter paraboloidal reflectors which are electronically connected to produce a array which can image astronomical objects.

Jeff Mangum

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How Long Does it Take the Sun to Orbit the Center of our Galaxy?

Question: How long does it take our sun to complete a full orbit around the super blackhole at the center of the Milky Way?  — Dustin

Answer: We can calculate this value by noting that the Sun is about 8 kilo-parsecs, or about 2.5×10^(17) km, from the center of our galaxy and travels at a speed of about 225 km/sec around the center of the galaxy.  Assuming that the Sun’s orbit about the center of the galaxy is circular, we know that the circumference of that circular orbit is 2*pi*r, where r is the distance from our Sun to the galactic center.  Since distance = rate * time, we know that time = (2*pi*r)/rate = (2*pi*2.5×10^(17) km)/220 km/sec =~ 225 million years.

Jeff Mangum

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How Do Very Large Antenna Arrays Synchronize and Work?

Question: How do very large antenna arrays synchronize with each other and why VLAs are used?  — Aloka

Answer: Let me point you to a nice description of how radio telescopes and radio telescope arrays work that has been produced by the National Radio Astronomy Observatory.  We connect radio telescopes together electronically so that each signal measured by each antenna is closely associated with the signals measured from every other antenna in an array.  We can then use a computer to put those signals together, which allows us to make a radio picture of the object that the array antennas were looking at.  We use very large arrays as they allow us to make higher spatial resolution measurements of objects.  The resolution attained by a radio telescope array is proportional to the distance between its individual antenna elements.  So, the farther apart we can put the antennas, the higher the resolution we have in our measurements.

Jeff Mangum

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Do Magnetars Have Solar Systems?

Question: Do magnetars have their own solar system, and do they attract iron rich asteroids? If so do their orbits have more of a magnetic attraction than a gravity one or both?  — Paul

Answer: Magnetars are not known to have planets or other solar system material orbiting them, so I do not believe that there is a significant amount of iron-rich material for a magnetar to attract.  Also, their gravitational forces are a much more serious concern than any magnetic attraction they might have to an object since magnetic attraction requires the proper polarity for objects to attract (or repel).

Jeff Mangum

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Recordings of Transmissions from the Decans of the Zodiac

Question: Do recordings of the transmissions from the decans of all twelve zodiac constellations exist anywhere? If so, are they available to the public.  — Toby

Answer: I suspect that by “decans” you are referring to the artificial demarcation system for the zodiac used in astrology.  Just so there is no confusion, “astrology” is not “astronomy”.  Astrology is not science and has no grounding in fact.  Astronomy is a branch of the physical sciences, which is one of the major science categories associated with how we describe the world and universe around us.  As to whether there are “recordings” of the physical objects which lie in the direction of the zodiac, the answer is in fact yes, if you count all of the astronomical measurements that scientists make of the myriad of objects in these directions in the sky.  These data are comprised of measurements of the brightnesses of stars, measures of the spectral structure (i.e. what kinds of atoms they are made of), measurements of the dust which surrounds many stars, etc.  You can sample these measurements from many online archives such as the SIMBAD database.

Jeff Mangum

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How Strong is the Signal from the Voyager 1 Spacecraft When it Reaches Earth?

Question: What is the signal strength in watts received by the VLBA that is transmitted from Voyager 1? I recall that Voyager 1 transmits at 22 watts and is nearly 20 billion km away, so how weak is the signal here?  — Robert

Answer: The answer to your question happens to be included in a story about the VLBA detecting Voyager 1 in 2014.  As you said, the radio strength of Voyager 1 is about 23 watts.  This signal is directed toward Earth, but since Voyager 1 is about 15 billion kilometers from Earth, by the time Voyager 1’s signal reaches us its power is less than an attowatt, or a billionth of a billionth of a watt.

Jeff Mangum

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Ideas for Converting an Old Observatory Into a Science Education Center

Question: Hi there!
I am an Interior Architecture student from Leeds Beckett university. Currently working on my final year project, I have to pick a building that is unused/abandoned and propose/design a new use for it.

I found Bidston Observatory built in 1866, used to determine the  time in Liverpool, Gravity measurements and astronomical observation (with a transit telescope and refracting telescope) it also used to rate chronometers. Eventually, the activity of the building focused on tide measurements and predictions, and the astronomical research and observation stopped in 1890.

I am proposing its revival by creating a space where people of all ages can gain interest in astronomy, mainly into the traditional or ancient techniques to calculate time, star mapping, and navigation.  In an interactive educational way.

I am looking into the possibility of making tools, learning to use them, and make star maps.

Do you have any ideas on activities that can bring this building back to life and help kids and teenagers to engage with astronomy? I am trying to stay away from the standard exhibitions with buttons that tell u stories, but trying to get kids to build, use tools, learn by making and experimenting.

Any ideas welcome!




Answer:  There are quite a few sources of ideas for educational astronomy activities that one can do either in a science education center (which is what you are developing) or at a small gathering of friends looking at the sky at night.

Hopefully you can find some exercises in the resources above that you can adapt to your science education center.  Let me know if you need additional suggestions for resources.

Jeff Mangum

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Do Black Holes Create Dark Energy?

Question: Hi, my name is Kemp and I just finished watching a program from the Discovery Channel entitled “Understanding the Universe”. The program triggered an odd question, do blackholes create dark energy and/or dark matter relative to their size?  — Kemp

Answer: No.  The only connection between black holes and dark energy is the “darkness” of their names.  Black holes are sources of intense gravity from which even light cannot escape.  Dark energy is the theoretical entity that accounts for the majority of the energy content of the universe and is responsible for the overall acceleration of the expansion of the universe.

Jeff Mangum

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